The term “vacuum systems” refers to special pneumatic conveyors. Generally speaking, in such conveyors transportation takes place in that a pressure difference is applied to the material to be conveyed, i.e. the material to be conveyed is entrained in the fluid flow generated as a result of the pressure difference, wherein generally air is used as the transport medium.
Especially in aircrafts, vacuum systems are used for the transportation of waste from the cabin, for example from toilets or galleys, to a central collecting tank. In this arrangement the material to be conveyed is conveyed to the collecting tank by way of a pipeline network. Negative pressure in the collecting tank in relation to the cabin pressure provides the required pressure difference.
In aircraft with pressurised cabins the pressure difference between the cabin and the environment is used directly to generate the negative pressure for pneumatic conveyance. When this pressure difference is insufficient, e.g. on the tarmac or at low altitudes, the required pressure difference is generated by a compressor.
In the case of toilets with a pneumatic conveyor system in aircraft systems, often a loud noise level arises. This noise is even noticed by the passengers in the cabin and is perceived by passengers to be uncomfortable.
Conventional measures to reduce the noise level at the feed-in location consist of closing the lid of the conveyance system prior to the flushing procedure so as to thereby keep the noise in check. Furthermore, attempts are made to instruct passengers by way of specific signage to take noise reduction measures such as for example to close the toilet lid. Up to now the kinetic energy of the material to be conveyed has been reduced at the inlet to the tank by means of tank inlet protection devices so as to prevent damage and wear.
However, up to now the above-described noise reduction measures have returned only moderate success, without effectively improving passenger comfort.